Fix MCP tool contracts

[portswigger-penguin]

Summary

• derive required fields from Kotlin constructor defaults and advertise nullable values accurately
• validate ports, pagination values, random-string length, regexes, and HTTP/2 pseudo-headers before calling Montoya
• accept whole JSON numbers such as 443.0 for integer parameters and ignore undeclared client arguments
• return actionable MCP error results instead of exceptions or success-shaped error strings
• exercise every advertised tool using only the fields its generated schema declares as required

Root cause

Schema generation treated Kotlin nullability as requiredness, while kotlinx.serialization treats constructor defaults as optionality. Nullable properties without defaults—most visibly tabName—were therefore advertised as optional but rejected during deserialization. Other constraints were neither represented in schemas nor checked consistently before reaching downstream APIs.

Impact

Schema-respecting MCP clients can omit optional values safely, clients that encode whole numbers as JSON decimals remain compatible, and invalid tool calls receive an MCP error with a concrete correction instead of an exception or successful-looking string.

Validation

• ./gradlew test
• generated-schema integration test invokes every Community and Professional tool with required fields only
• focused coverage for integer coercion, nullable schemas, numeric constraints, regex errors, ports, pagination, and HTTP/2 pseudo-headers
• fresh assertion-quality audit completed

Closes #109